Pain behaviors before and after treatment of oral disease in cats using video assessment: a prospective, blinded, randomized clinical trial.

BACKGROUND: Specific behaviors associated with pain in cats with oral disease have not been consistently studied. The aim of this exploratory study was to identify pain-induced behaviors in cats before and after treatment of oral disease using video assessment. Twenty-four cats (6 ± 3.3 years old; 4.9 ± 1.7 kg) were included in a prospective, blinded, randomized clinical trial. Cats were equally divided into minimal (G1: minimal dental treatment) or severe (G2: multiple dental extractions) oral disease groups. After acclimation at day 0, they underwent oral examination, radiographs, scaling, and dental extractions under general anesthesia (anesthetic protocol: acepromazine, hydromorphone, propofol, isoflurane, meloxicam, and local anesthetic blocks; day 1), and were discharged at day 6. Cats were filmed remotely for 10 min using a wide-angle glass lens camera before surgery (baseline) and throughout the study at different time points (36 h of video recording). The videos consisted of four parts namely general, playing, feeding and post-feeding behaviors. A board-certified behaviorist evaluated the duration/frequency of different behaviors based on an ethogram, which were analyzed using linear mixed models and a generalized linear model, respectively (p < 0.05). RESULTS: In comparison with baseline, duration of "not pawing the face" was significantly shorter at day 3 in G2. These cats spent significantly longer time "standing" and "laying" at days 3 and 6, respectively; G1 spent significantly less time "walking" and "standing" at days 3 and 4, respectively and significantly longer time "immobile" at day 3. Duration of "no/slow tail movement" was significantly longer in G2 than G1 at day 5. Duration of "pawing the ribbon" (playing) was significantly shorter in G2 than G1 at day 1. Feeding and post-feeding behaviors with soft food were not significantly different between groups or over time. Frequency of "difficulty grasping dry food" was significantly higher in G2 than G1 up to day 6. Frequency of post-feeding "head shaking" was significantly higher in both groups at day 6 when compared with baseline. CONCLUSIONS: This study identified pain-induced behaviors in cats undergoing treatment of oral disease. These behaviors may be used to differentiate painful versus pain-free cats in clinical practice.

Analgesic efficacy of laser acupuncture and electroacupuncture in cats undergoing ovariohysterectomy.

The aim of this study was to compare the effects of laser acupuncture and electroacupuncture on postoperative pain and analgesic requirements in cats. In a prospective, randomized and blinded clinical study, thirty cats undergoing ovariohysterectomy were sedated with intramuscular (IM) ketamine (5 mg/kg), midazolam (0.5 mg/kg), and tramadol (2 mg/ kg). Before the induction of anesthesia, the animals were randomly distributed into three groups of ten cats each: LA: bilateral Stomach 36 (ST-36) and Spleen 6 (SP-6) acupoints were stimulated with an infrared laser; EA: bilateral ST-36 and SP-6 acupoints were stimulated with an electrical stimulus; Control: no acupuncture was applied. Postoperative analgesia was evaluated in the first 24 hr post-extubation using the Interactive Visual Analogue Scale and UNESP-Botucatu Multidimensional Composite Pain Scale. Rescue analgesia was provided with IM tramadol (2 mg/kg), and the pain scores were reassessed 30 min after the rescue intervention. If the analgesia remained insufficient, meloxicam (0.2 mg/kg IM, single dose) was administered. Data were analyzed using t-tests, the Mann-Whitney U test, and Friedman test. P<0.05 was considered significant. The pain scores did not significantly differ between the treatment groups at any time point (P>0.05). The prevalence of rescue analgesia was significantly higher in the Control group than in the LA and EA groups (P=0.033). Preoperative laser and electroacupuncture reduced the need for rescue analgesia during the first 24 hr after ovariohysterectomy.

Yamamoto New Scalp Acupuncture for postoperative pain management in cats undergoing ovariohysterectomy.

OBJECTIVE: To evaluate the analgesic efficacy of Yamamoto New Scalp Acupuncture (YNSA) as an adjuvant for postoperative pain management in cats. STUDY DESIGN: Prospective, randomized, blinded, clinical study. ANIMALS: Twenty cats aged (mean ± standard deviation) 25 ± 9 months and weighing 2.7 ± 0.6 kg undergoing ovariohysterectomy. METHODS: The cats were sedated with intramuscular (IM) ketamine (5 mg kg-1), midazolam (0.5 mg kg-1) and tramadol (2 mg kg-1). The cats were randomly distributed before induction of anesthesia into two groups of 10 cats each: group YNSA, in which bilateral basic D points were stimulated with a dry needle from 20 minutes prior to anesthetic induction to the end of the surgery; group Control, in which no acupuncture was applied. Postoperative analgesia was assessed at 1, 2, 4, 8, 12, 18 and 24 hours postextubation using an Interactive Visual Analog Scale and Universidade Estadual Paulista-Botucatu Multidimensional Composite Pain Scale (UNESP-Botucatu MCPS). Rescue analgesia was provided with IM tramadol (2 mg kg-1), and the pain scores were reassessed 30 minutes after rescue intervention. If the analgesia remained insufficient, meloxicam (0.2 mg kg-1 as a single dose) was administered IM. Data were analyzed using Student t-test, Fisher exact test, Mann-Whitney U test and Friedman test (p < 0.05). RESULTS: Significantly lower pain scores were observed in YNSA when compared with Control at 1-4 hours based on the UNESP-Botucatu MCPS scores. Although significant differences were not identified between groups requiring rescue analgesia, additional postoperative analgesia was administered to four of 10 cats in Control and no cats in YNSA. CONCLUSION AND CLINICAL RELEVANCE: Perioperative YNSA resulted in decreased pain scores and a reduction in postoperative requirement for rescue analgesia in cats. This method should be considered a viable option as an adjuvant analgesic therapy for cats undergoing ovariohysterectomy.

Effect of pre-warming on perioperative hypothermia and anesthetic recovery in small breed dogs undergoing ovariohysterectomy.

This study compared perianesthetic body temperatures and times to recovery from general anesthesia in small dogs that were either warmed for 20 minutes prior to anesthesia or not warmed. Twenty-eight client-owned dogs that were presented for ovariohysterectomy were included in the study. Small (<10 kg body weight) dogs with normal circulatory status were randomly assigned to receive pre-warming for 20 minutes or no treatment. Body temperature was measured during the procedure using a calibrated rectal probe. Duration of anesthesia and surgery, time to rescue warming, time to extubation, presence and duration of shivering, and time to return to normal temperature were recorded. Temperature at the end of surgery was significantly higher in the control group than the pre-warmed group. There was no difference in time to extubation or duration of postoperative shivering between groups. Pre-warming did not result in improved temperature or recovery from anesthesia.

Effet du préchauffement sur l'hypothermie périopératoire et le réveil après l'anesthésie chez des chiennes de petites races subissant une ovario-hystérectomie. Cette étude a comparé les températures corporelles périanesthésiques et la durée du réveil après l'anesthésie générale chez des petites chiennes qui étaient soit réchauffées pendant 20 minutes avant l'anesthésie ou non réchauffées. Vingt-huit chiennes appartenant à des clients qui ont été présentées pour l'ovario-hystérectomie étaient incluses dans l'étude. Les petites chiennes (< 10 kg de poids corporel) avec un état circulatoire normal ont été assignées au hasard pour recevoir le préchauffement de 20 minutes ou aucun traitement. La température corporelle a été mesurée durant l'intervention à l'aide d'une sonde rectale calibrée. La durée de l'anesthésie et de la chirurgie, le temps jusqu'au réchauffement de secours, le temps jusqu'à l'extubation, la présence et la durée des frissons et le temps jusqu'au retour à la normale ont été consignés. La température à la fin de la chirurgie était significativement supérieure dans le groupe témoin comparativement au groupe préchauffé. Il n'y avait aucune différence au niveau du temps jusqu'à l'extubation ni de la durée des frissons postopératoires entre les groupes. Le préchauffement n'a pas amélioré la température ni le réveil après l'anesthésie.(Traduit par Isabelle Vallières).

Influence of music and its genres on respiratory rate and pupil diameter variations in cats under general anaesthesia: contribution to promoting patient safety.

OBJECTIVES: The aims of the study were to recognise if there is any auditory sensory stimuli processing in cats under general anaesthesia, and to evaluate changes in respiratory rate (RR) and pupillary diameter (PD) in anaesthetised patients exposed to different music genres, while relating this to the depth of anaesthesia. METHODS: A sample of 12 cats submitted for elective ovariohysterectomy was exposed to 2 min excerpts of three different music genres (classical [CM], pop [PM] and heavy metal [HM]) at three points during surgery (T1 = coeliotomy; T2 = ligature placement and transection of the ovarian pedicle; T3 = ligature placement and transection of the uterine body). A multiparametric medical monitor was used to measure the RR, and a digital calliper was used for PD measurement. Music was delivered through headphones, which fully covered the patient's ears. P values <0.05 were considered to be statistically significant. RESULTS: Statistically significant differences between stimuli conditions for all surgical points were obtained for RR (T1, P = 0.03; T2, P = 0.00; T3, P = 0.00) and for PD (T1, P = 0.03; T2, P = 0.04; T3, P = 0.00). Most individuals exhibited lower values for RR and PD when exposed to CM, intermediate values to PM and higher values to HM. CONCLUSIONS AND RELEVANCE: The results suggest that cats under general anaesthesia are likely to perform auditory sensory stimuli processing. The exposure to music induces RR and PD variations modulated by the genre of music and is associated with autonomic nervous system activity. The use of music in the surgical theatre may contribute to allowing a reduced anaesthetic dose, minimising undesirable side effects and thus promoting patient safety.

A pilot study exploring the effects of musical genres on the depth of general anaesthesia assessed by haemodynamic responses.

OBJECTIVES: This pilot study aimed to investigate whether and how music and musical genres may influence the depth of anaesthesia, as measured using changes in arterial blood pressure (ABP), including systolic blood pressure (SBP), and heart rate (HR) across three different surgical time points. METHODS: This work focused on a sample of 12 female cats (Felis catus) that were subjected to an elective ovariohysterectomy (OVH), and three different surgical time points were considered (T1, coeliotomy; T2, ligature placement and transection of the ovarian pedicle; and T3, ligature placement and transection of the uterine body). All of the cats were subjected to stimulation with 2 min segments of three music tracks from different genres (pop [PM], classical [CM] and heavy metal [HM]). At the same time, ABP and HR measurements were obtained using a multi-parametric monitor. For statistical analysis, P values <0.05 were considered significant. RESULTS: For all cats, music exposure induced statistically significant changes in the parameters under study; the same finding was observed for the genre of music. The majority of cats experienced the same variation pattern, with lower values when exposed to CM, intermediate values when exposed to PM and higher values when exposed to HM. CONCLUSIONS AND RELEVANCE: Our results indicate that the development of sensory processing of acoustic stimuli is maintained by cats under general anaesthesia and reveal the influence of music on the autonomous nervous system, as measured using HR and SBP.

Comparison of thermoregulatory devices used during anesthesia of C57BL/6 mice and correlations between body temperature and physiologic parameters.

General anesthesia affects several body systems, including thermoregulation. Decreased body temperature during anesthesia has potential negative effects, including delayed recovery to consciousness. Thermoregulatory support devices are used to maintain temperature in anesthetized rodents. We analyzed 2 novel thermoregulatory devices, thermogenic gel packs and reflective foils, to compare their effectiveness in maintaining temperatures with that of a standard circulating-warm-water blanket (CWWB) in C57BL/6 mice. Mice were grouped randomly: control (no thermal support), reflective foil, gel pack, gel pack plus reflective foil, CWWB on medium setting, CWWB on high setting, and CWWB on high setting plus reflective foil. Mice were anesthetized with isoflurane for 30 min, and temperature and heart and respiratory rates were monitored. Results indicated that the temperatures of mice with reflective foil only (start temperature, 36.2 ± 0.38 °C; end temperature, 28.8 ± 0.78 °C) did not differ significantly from those of control mice; however, the inclusion of foil heightened thermogenic properties when combined with other devices. Thermogenic gel packs and CWWB on high setting, both with and without reflective foil, caused significant temperature increases (that is, 1.6 °C to 4.4 °C) in mice. CWWB on medium setting (blanket temperature, 37.5 °C) maintained mice at temperatures within 1 °C of the 36.1 °C baseline. Strong correlations existed between temperature, heart and respiratory rates, and recovery time to consciousness. This information provides guidance regarding the use of thermoregulatory devices in anesthetized rodents and demonstrates the effect of maintaining a consistent core temperature on physiologic parameters.

Neuropeptide alterations in the tree shrew hypothalamus during volatile anesthesia.

Neuropeptides are critical signaling molecules, involved in the regulation of diverse physiological processes including energy metabolism, pain perception and brain cognitive state. Prolonged general anesthesia has an impact on many of these processes, but the regulation of peptides by general anesthetics is poorly understood. In this study, we present an in-depth characterization of the hypothalamic neuropeptides of the tree shrew during volatile isoflurane/nitrous oxide anesthesia administered accompanying a neurosurgical procedure. Using a predicted-peptide database and hybrid spectral analysis, we first identified 85 peptides from the tree shrew hypothalamus. Differential analysis was then performed between control and experimental group animals. The levels of 12 hypothalamic peptides were up-regulated following prolonged general anesthesia. Our study revealed for the first time that several neuropeptides, including alpha-neoendorphin and somatostatin-14, were altered during general anesthesia. Our study broadens the scope for the involvement of neuropeptides in volatile anesthesia regulation, opening the possibility for investigating the associated regulatory mechanisms.

Evaluation of inflammatory and hemostatic surgical stress responses in male cats after castration under general anesthesia with or without local anesthesia.

OBJECTIVE: To characterize acute inflammatory and hemostatic surgical stress responses following castration in cats and to evaluate whether the addition of local anesthesia to the anesthetic protocol attenuates these responses. ANIMALS: 39 male cats. PROCEDURES: Cats undergoing castration were randomly assigned to 2 groups: both groups underwent surgery with general anesthesia, and 1 group additionally received a local anesthetic (lidocaine [2.0 mg/kg in total, divided intratesticularly and SC]) prior to incision. Blood samples were collected after anesthetic induction (baseline) and 1, 5, and 24 hours later. Thromboelastography and coagulation variables (activated partial thromboplastin time [aPTT] and prothrombin time [PT]) were analyzed; fibrinolysis was assessed with plasma D-dimer concentrations. The acute-phase response was evaluated via measurement of plasma fibrinogen and serum amyloid A (last time point, 28 hours) concentrations. Hematologic variables were analyzed at baseline and 1, 5, and 24 hours later. RESULTS: Evidence of hemostatic and inflammatory activation after surgery was detected in both groups. Maximum amplitude and G (global clot strength) were significantly increased at 24 hours, and significant, but not clinically relevant, decreases were detected in aPTT at 5 and 24 hours and in PT at 24 hours, compared with baseline values. Serum amyloid A concentrations were significantly higher at 24 and 28 hours than at baseline, and plasma fibrinogen concentration was significantly increased at 24 hours; WBC and RBC counts and Hct were significantly increased at multiple time points. No differences between groups were detected for any variables. CONCLUSIONS AND CLINICAL RELEVANCE: Castration appeared to induce hypercoagulability and an acute-phase inflammatory response in cats. Local anesthesia with lidocaine did not attenuate this response.

Effect of anaesthesia with clove oil in fish (review).

Clove oil is an effective, local and natural anaesthetic. Many hatcheries and research studies use clove oil to immobilize fish for handling, sorting, tagging, artificial reproduction procedures and surgery and to suppress sensory systems during invasive procedures. Clove oil may be more appropriate for use in commercial aquaculture situations. Improper clove oil use can decrease fish viability, distort physiological data or result in mortalities. Because animals may be anaesthetized by unskilled labourers and released in natural water bodies, training in the proper use of clove oil may decrease variability in recovery and experimental results and increase fish survival. Here, we briefly describe many aspects of clove oil, including the legal uses of it, anaesthesia mechanism and what is currently known about the preparation and behavioural and pathologic effects of the anaesthetic. We outline methods and precautions for administration and changes in fish behaviour during progressively deeper anaesthesia and discuss the physiological effects of clove oil, its potential for compromising fish health and effectiveness of water quality parameters.

Effect of a heat and moisture exchanger on heat loss in isoflurane-anesthetized dogs undergoing single-limb orthopedic procedures.

OBJECTIVE: To determine whether a heat and moisture exchange device (HME) prevents a decrease in body temperature in isoflurane-anesthetized dogs undergoing orthopedic procedures. DESIGN: Blinded randomized controlled clinical trial. ANIMALS: 60 privately owned dogs weighing at least 15 kg (33 lb). PROCEDURES: Dogs were randomly assigned to 1 of 3 treatment groups (n = 20/group): HME placed immediately after anesthetic induction with isoflurane, after transfer to the operating room, or not at all. The device consisted of a hygroscopic filter placed between the endotracheal tube and the Y piece of the anesthesia circuit. Each dog was positioned on a circulating warm water blanket and had a forced-air warming blanket placed over its body. Body temperature was monitored after transfer to the operating room with a probe placed in the thoracic aspect of the esophagus. RESULTS: Study groups did not differ significantly with respect to body weight, body condition score, reproductive status, breed, surgical procedure, preoperative sedative and opioid administration, anesthetic induction drug, local nerve block technique, or operating room assignment. There were no significant differences among groups in esophageal temperature variables, interval between anesthetic induction and surgery, surgery duration, anesthesia duration, or oxygen flow rate. However, the relationship between temperature delta and body weight was significant and relevant (R(2) = 0.23), as was the association between temperature nadir and body weight (R(2)= 0.10). As body weight increased, the temperature delta decreased and temperature nadir increased. No other significant relationships were identified. CONCLUSIONS AND CLINICAL RELEVANCE: Inclusion of an HME in healthy dogs undergoing anesthesia for an elective orthopedic surgery did not facilitate maintenance of body temperature throughout the procedure.

Nictitating membrane resection in the horse: a comparison of long-term outcomes using local vs. general anaesthesia.

REASONS FOR PERFORMING STUDY: Neoplasia, for which surgical excision is a frequent treatment, is the most common disease of the equine nictitating membrane. There is little long-term follow-up information available to the practitioner regarding the long-term effects of nictitating membrane excision on ocular health. No information is available to compare recurrence of primary neoplasia of the nictitating membrane after excision with local or general anaesthesia. OBJECTIVES: To evaluate the long-term complications of nictitating membrane resection in horses; recurrence of neoplasia of the nictitating membrane when nictitating membrane resection is performed under local vs. general anaesthesia and if the method of anaesthesia used to permit resection of the affected membrane influences the recurrence of neoplasia of the nictitating membrane after complete nictitating membrane resection. METHODS: Records of 26 horses receiving resection of the nictitating membrane for primary neoplasia of the nictitating membrane 1999-2009 were reviewed. Clinical examination findings, surgical procedure, anaesthesia type, histopathological findings and details of adjunctive treatment were recorded. Owners were contacted via telephone regarding post operative outcomes. Data were analysed using a Fisher's exact test (P<0.05). RESULTS: The most common long-term complication of nictitating membrane excision was mild ocular discharge. Squamous cell carcinoma was the most frequent histopathological diagnosis. Recurrence of neoplasia was uncommon (2/26 horses). No significant difference in the number of horses experiencing recurrence of neoplasia was detected between groups receiving general anaesthesia vs. those receiving local anaesthesia. CONCLUSIONS: Resection of the nictitating membrane in horses following local anaesthesia is not associated with increased risk of recurrence of neoplasia compared with excision under general anaesthesia. Resection of the nictitating membrane is not associated with any long-term ocular side effects and can be an effective modality for cure of primary neoplasia of the nictitating membrane in selected cases.

Physiologic evaluation of capture and anesthesia with medetomidine-zolazepam-tiletamine in brown bears (Ursus arctos).

Physiologic variables during anesthesia with medetomidine-zolazepam-tiletamine were evaluated in 52 free-ranging brown bears (Ursus arctos) darted from a helicopter and in six captive brown bears darted at a zoo. During anesthesia, rectal temperature, respiratory rate, heart rate, and pulse oximetry derived hemoglobin oxygen saturation were recorded. Arterial blood samples were collected and immediately analyzed for evaluation of pulmonary gas exchange, acid-base status, and selected hematologic and plasma variables. At the end of anesthesia, atipamezole was administered intramuscularly at five times the medetomidine dose. Capture-induced hyperthermia and lactic acidemia were documented in free-ranging bears. Hypoxemia during anesthesia was documented in both free-ranging and captive bears. In free-ranging bears, rectal temperature, heart rate, lactate, hematocrit, and hemoglobin decreased significantly during anesthesia, whereas partial pressure of arterial carbon dioxide, pH, potassium, and glucose increased. Yearlings had a significantly higher heart rate, pH, base excess, bicarbonate, and glucose, and had a significantly lower rectal temperature, sodium, hematocrit, and hemoglobin when compared with subadult and adult brown bears. In conclusion, alterations in pulmonary gas exchange and acid-base status in brown bears during anesthesia with medetomidine-zolazepam-tiletamine with the doses and capture methods used in this study were identified. Oxygen supplementation is recommended to counteract hypoxemia during anesthesia.

Chemical restraint, anesthesia, and analgesia for camelids.

This article covers techniques used to provide chemical restraint, injectable or inhalation anesthesia, and analgesia in camelid patients. Understanding the information presented improves safety and efficacy when using the techniques presented in the article. This article focuses primarily on llama and alpaca patients. Of the techniques that have been used on camels, the dosing protocols provided have proven effective.

An endoscopic method for identifying sex of hatchling Chinese box turtles and comparison of general versus local anesthesia for coelioscopy.

OBJECTIVE: To establish a safe and effective endoscopic method for visualizing the gonads and identifying the sex of hatchling Chinese box turtles and to compare the effects of general versus local anesthesia during coelioscopy. DESIGN: Clinical trial. ANIMALS: 58 hatchling Chinese box turtles (Cuora flavomarginata). PROCEDURES: Turtles were randomly assigned to be anesthetized with a mixture of ketamine, medetomidine, and morphine (n = 29) or to receive local anesthesia with lidocaine in the prefemoral region (29). Coelioscopy was performed with a rigid 1.9- or 2.7-mm telescope following insufflation with sterile lactated Ringer's solution. Ease of endoscopic sex identification and quality of anesthesia were scored. Body weights were recorded before and 7 and 14 days after surgery. RESULTS: Gonads were easily visualized and sex was easily identified in all 58 turtles without complications. Endoscopy scores and pre- and postoperative weights did not differ significantly between groups. However, anesthesia scores were significantly worse for animals that received local anesthesia alone, compared with those that underwent general anesthesia. All anesthetized turtles recovered within 21 minutes after administration of the reversal agents, atipamezole and naloxone. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that coelioscopy with a rigid endoscope and lactated Ringer's solution for insufflation was a safe and effective method for identifying the sex of hatchling Chinese box turtles. General anesthesia was effective and effects were rapidly reversible; local anesthesia with lidocaine alone was considered insufficient for coelioscopy.

Regional anesthesia as an adjunct for eyelid surgery in dogs.

Eyelid surgery plays an important role in the management of a variety of ophthalmic diseases. Surgery on the adnexa and eye is routinely performed on an anesthetized patient. Minor procedures, such as conjunctival biopsy, may be performed in an awake patient using only topical anesthesia. Retrobulbar, peribulbar, and local anesthesia are less commonly used in general practice; however, they can provide significant advantages when used appropriately. Advantages to local anesthesia/sedation include being able to perform some ophthalmic procedures without having to place the patient under general anesthesia, ability to maintain the patient under a lighter plane of general anesthesia, improved postoperative comfort, and potentially smoother recoveries from general anesthesia. This article reviews this author's current indications and techniques for regional anesthesia as an adjunct to eyelid surgery in dogs.

Influence of antibiotic therapy on serum levels of reactive oxygen species in ovariectomized bitches.

This study was conducted on 60 ovariectomized bitches. The objectives were to measure the mean reactive oxygen species (ROS) concentrations before, during and after surgery, and to investigate the effect of the administration of five different antibiotic treatments: amoxicillin, benzylpenicillin/dihydrostreptomycin, sulfametazine/sulfamerazine/sulfathiazole, enrofloxacin, lincomycin/spectinomycin. The first value recorded represented the mean ROS concentration in anestral bitches and constitutes a reference level with which to compare the subsequent measurements. After premedication, induction of anesthesia and during maintenance and surgery, ROS serum concentrations showed constant values until the end of surgery. After surgery and during antibiotic administration, an increase in ROS concentration occurred, which differed among the five groups in relation to the antibiotics employed. The lowest increases occurred in the groups treated with the combination of lincomycin/spectinomycin, and with amoxicillin; whereas the highest increases were detected in the group treated with enrofloxacin. The three other antibiotics showed an intermediate level of influence on oxidative status.

Effects of anesthesia on DPOAE level and phase in rats.

Many studies of the auditory system are performed on animals under general anesthesia. A concern for researchers is that these agents may significantly alter the underlying neurophysiologic mechanisms being studied. The effects may very across species, and even among individuals within a species. An investigation was undertaken to study whether DPOAE measures differ using three different anesthetic regimens: acetylpromazine-ketamine, xylazine-ketamine, and sodium pentobarbital. The same rat was anesthetized in three consecutive weeks using a different anesthetic regimen each week. DPOAE magnitude and phase temporal responses were recorded from which several measures were taken: DPOAE levels at the onset of the primaries, changes in DPOAE level as a function of time during presentation of the primaries (DeltaLI) and changes in DPOAE level (DeltaLC) and phase (DeltaPC) during presentation of a broad-band noise presented contralateral to the probe. Each week the same measurements were repeated with the rat anesthetized using a different regimen and at the end of the third week, the middle ear muscles were sectioned and the measurements repeated once again. Results showed that the anesthetic regimens did not differentially alter the DPOAE onset levels. When sodium pentobarbital was used as the anesthetic regimen, DeltaLC and DeltaPC were significantly smaller relative to those measured when the rats were anesthetized with acetylpromazine-ketamine and xylazine-ketamine. Based on the assumption that large, positive (DeltaPC) values are related to middle ear muscle activation, the middle ear muscle reflex remained at least partially active in some rats under sodium pentobarbital anesthesia. The DeltaLI measures were significantly smaller when the animals were anesthetized with xylazine-ketamine and sodium pentobarbital than when they were anesthetized with acetylpromazine-ketamine. Recordings taken after sectioning the middle ear muscles suggested that the middle ear muscle reflex substantially contributes to DeltaLC and DeltaPC measures under the anesthetic regimens xylazine-ketamine and acetylpromazine-ketamine. Data indicated that anesthetic agents variably alter neurophysiologic mechanisms involved with the complex control of the auditory signal even among individuals in the same species. Extreme care should be taken when comparing DeltaLI, DeltaLC and DeltaPC across studies when different anesthetic regimens are used within and across species.

Stress responses in adult cattle due to surgical dehorning using three different types of anaesthesia.

Dehorning adult cattle is a surgical procedure causing distress of varying intensities that can be reflected in behavioural changes and alterations in plasma cortisol levels. Stress responses during the dehorning process were evaluated in 18 Red Pied cows. The cows were divided into 3 groups of six and kept in tie-stall housing. Those in the first group were dehorned under general anaesthesia (GA) induced by intravenous administration of xylazine and ketamine. The second group was dehorned under sedation and local anaesthesia (SLA) induced by intramuscular administration of xylazine and local anaesthesia with lidocaine. The third group was dehorned under local anaesthesia (LA) with lidocaine. Dehorning was performed with a foetotomy wire. Blood samples were taken 0.5 h before dehorning to determine cortisol levels, and, by means of a central venous catheter inserted into the jugular vein, during surgery at 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 5, 6, 7 and 8 h post-surgery. Concurrently, occurrence of stress behaviours was assessed. Cortisol levels were measured by enzyme immunoassay (EIA). The lowest mean peak levels of plasma cortisol (82.53 +/- 6.04 nmol l(-1)), the most rapid return of plasma cortisol levels to baseline values (1.92 +/- 1.11 h), and the lowest occurrence of stress behaviours (2.38 +/- 5.83%) were noted in the SLA group. The highest mean peak levels plasma cortisol (113.86 +/- 25.65 nmol l(-1)), the slowest return of plasma cortisol levels to baseline values (3.83 +/- 2.18 h) and the most frequent occurrence of stress behaviours (65.48 +/- 28.72%) were observed in the LA group. There were significant differences between the SLA and LA groups in peak plasma cortisol levels (p = 0.011) and in occurrence of stress behaviours (p = 0.003). Sedation induced by intramuscular administration of xylazine in conjunction with local anaesthesia with lidocaine is considered the most suitable method of anaesthesia when dehorning adult cattle. Local anaesthesia with lidocaine alone was least suitable.